DEVELOPMENT OF A NEW TYPE OF COMPOSITE UNDERSPANNED BEAM

摘要

This paper describes the design of the structure of a multi-story industrial building. The selected structural system is composed of steel underspanned beams, prefabricated concrete elements and a layer of cast-in-place concrete. The 12.5 m long principal beams are spaced every 2.5 m and supported on 7.5 m support beams of similar construction. The upper chords of the principal beams, which are triangular in shape and include a ribbed reinforcing bar, are integrated within the thickness of the concrete slab. Composite behaviour is attained through adhesion of the reinforcing bar. No formwork is required in the assembly. The technical and economical advantages of the structural system result from innovative solutions adopted to satisfy the modularity of the project, the need for large spaces free of columns, the high dynamic service loads and the density of the technical installations. A dynamic analysis showed the sensitivity of the composite floors to vibrations. A cracking analysis showed that such a system consisting of steel beams embedded in the concrete resulted in a high probability of appearance of large cracks concentrated at the locations of the discontinuities. Tests conducted on a prototype permitted the verification of the various hypotheses related to the resistance, rigidity, cracking and dynamic behaviour of the composite structural system.